During a procedure that uses multiple imaging modalities, for example CT and live X-ray, a physician will need to register the modalities. In common applications that use manual 2D-3D registration, this is done in the following manner: The physician moves a C-arm to a certain angulation that gives him a clear view on landmarks in the body that can be used for registration, for example the pelvic bone. He will then acquire an exposure run or a single shot image. Next, the physician will move the C-arm to a different angulation that is sufficiently different (more than 45 degrees difference) and shoot another exposure or single shot.
Both X-ray runs are shown in different viewports of the application, where they are blended with appropriately rotated volume views of the CT volume. The physician will now move the CT in both views such that it optimally overlaps the live X-ray. The visual markers that the physician uses to determine optimal overlap are usually bony landmarks, such as the pelvis, spine or ribcage.
WO 2013/132402 A2 discloses hereto a system for image registration. It includes an image feature detection module configured to identify internal landmarks of a first image. An image registration and transformation module is configured to compute a registration transformation, to register a second image with the first image based on surface landmarks to result in a registered image. A landmark identification module is configured to overlay the internal landmarks onto the second image using the registration transformation, encompass each of the overlaid landmarks within a virtual object to identify corresponding landmark pairs in the registered image, and register the second image with the first image using the registered image with the identified landmarks.